Champion Grades

So just out of curiosity, is there something perhaps wrong with the grades that you get post game updating to your champ collection page? It's pretty meaningless but I've noticed I might get an s or something from a game and check to see that my season best on a champ under my collection says b+ or whatever even though 3 days may have passed. Perhaps a visual bug? I dunno... Hopefully a Riot person could reply to this and give an answer. It would be cool, thanks.